Start at the iliac crest (the top of your hipbone that you can feel like a shelf on the side of your body). From this level on your spine, measure to the C7 vertebrae, the knobby bone at the base of your neck when you put your head down. Make sure to keep your back straight while having the measurement taken.

100% Recommendation

Great day pack - I've been a fan of Osprey since using my Kestrel for several years now - great design, light weight, loaded with pockets, easy to pack and access - and I love the whistle! Keep it up osprey - you cannot go wrong this pack.